1. Field of Invention
This invention relates to an improved apparatus and method of thawing frozen blood, blood plasma, or other temperature sensitive biological fluids. Storing blood plasma in the frozen state and thawing it as needed is a common practice in hospitals and blood banks. Because plasma or blood can only be used for a relatively short time after thawing, it is thawed in response to a specific patient's need. The need for such blood products is often urgent, making it important to thaw blood products rapidly but without overheating to prevent damage to the fluid during the thawing process.
2. Description of Prior Art
For a number of years it was common practice to thaw frozen plasma for use by placing the bag directly into a controlled temperature warm water bath, sometimes with agitaion of the water to increase heat transfer. More recently that method has been abandoned because of the possibility of contamination of the water bath with bacteria or other hazardous materials, which in turn could contaminate the access ports of the plasma bag. When the bag is accessed by an intravenous system component, the contaminant might be passed on to the patient receiving the transfusion.
U.S. Pat. No. 6,007,773 discloses a system for thawing blood plasma in which the plasma bag is first inserted into a thin waterproof bag and then immersed in a warm water bath. The outer bag, open on top and vented to atmosphere, isolates the plasma bag from contamination while adding some thermal resistance to convective warming of the plasma bag. Actively generated water currents exert a kneading effect on the thawing plasma bag to increase heat transfer.
While the technique previously described improved upon earlier methods, the need remains for a frozen plasma thawing system which can safely further reduce thawing time.
Although the current water bath method protects against contamination and employs water currents to increase convective warming, heating rates to the plasma bag are unnecessarily limited by thermal resistance in the added thin isolating bag and the water boundary layer outside the thawing bag.